Three-dimensional stereo perception is produced on the basis of multiple depth cues, mainly including binocular disparity, motion parallax and accommodation. Those optical devices that are able to generate binocular disparity on human eyes can produce three-dimensional stereo vision. Three-dimensional display technology is in wide use, and has a bright prospect in a variety of fields, including medicine, geospatial intelligence, oil exploration, pharmaceutical manufacturing, construction, movie and television entertainment, video communication, science presentation, commodity advertisements, etc.
Currently, three-dimensional display technologies mainly include stereoscopic three-dimensional display, autostereoscopic three-dimensional display, holographic three-dimensional display and volumetric three-dimensional display.
The implementation of stereoscopic three-dimensional display requires the visual aids like glasses, which enable the observer to see images with binocular disparity, thus generating stereo vision. Today, this method mainly includes complementary colors or polarizations, which are widely applied to 3D films and other fields. However, this method requires the assistance of external tools to achieve, and 360° view is not achievable. Long-time watching may cause visual fatigue and other symptoms to people's eyes.
Autostereoscopic display is a three-dimensional display technology, which enable the observer to see images with binocular disparity but without the help of external tools. This method mostly adopts parallax slit and other means to enable observers to watch at certain areas with naked eyes to perceive three-dimensional vision.
Holographic three-dimensional display is implemented based on the principle of “interference records and diffraction reappears”. Holographic three-dimensional display records all vibration amplitude and phase information of object light waves. Thus, it is an ideal way for three-dimensional display. However, this method demands enormous data storage and information transformation. Dynamic holographic display has not been achieved yet because of the technological limitation.
Volumetric three-dimensional display is realized by controlling brightness of each voxel scattered in the volume space. Swept volume three-dimensional display scans the three-dimensional profile of the objects in the volume space through volume sweep/scanning and achieves three-dimensional display of the objects as a result of persistence-of-vision effect. This method provides both horizontal and vertical parallax, allowing for horizontal 360° round-viewing, which is suitable for multiple people to watch by naked eyes. However, volumetric three-dimensional display has the characteristics of non-occlusion, i.e., the occluding relation between two objects in the volume space, where one object is in front of or blocks the view of the other object, cannot be displayed. Thus, this method can only display transparent objects, but cannot achieve perspective occlusion of objects in a volume space.
Based on the above analysis on current three-dimensional display technologies, improvements are in urgent demand in this field.